Add gas tank vent?

[Dave 53]

Been reading the threads about the difficulty with putting gas in the tank due to the filler pipe entering the tank half way up instead of at the top combined with vent issues. It seems there are two kit supplies tanks, old and new. My kit was delivered 2/18. Do I have the new tank? How big of an issue is this? Seems a good solution is to tap a vent pipe on top of the tank to the top of the filler neck. I need to remove my fire wall behind the driver's seat to redo something, so if this venting solution is a must do, this would be a good time to pull the passenger side firewall too, pull the gas tank and add a vent line. Should I add the vent pipe or is it not a big deal?

[Hobby Racer]

A vent is a good idea, not just for easier, faster filling but to allow the tank to "breath". When the tank heats up the excess pressure needs to vent someplace and when it cools down it needs to pull air in to equalize the pressure. Think of a plastic 5 gallon gas jug left sealed in the sun. It expands and blows out the sides. Similarly in the cold it collapses the sides.

[aquillen]

The old tank was a consistent shape all the way across and from front to back. The new tank was cut out front to back somewhat on the driver side so that seat could go back further = more leg room up front.

[Dave 53]

Seems like the vent system is set up for slow changes in fuel level like as it's burned off or due to temperature changes. The issue I'm concerned about is overloading the vent system when the fuel level is changing rapidly, like when pumping gas in at the gas station. I see some threads about this issue, but not much, so I'm confused if it's a serious problem and adding a vent from the top of the tank to the top of the filler neck is a must do fix.

[Ajzride]

Might depend on if you are in a state that requires sealed gas pumps, I’ve had no issues so far with an old school gas pump.

[Hobby Racer]

Seems like the vent system is set up for slow changes in fuel level like as it's burned off or due to temperature changes. The issue I'm concerned about is overloading the vent system when the fuel level is changing rapidly, like when pumping gas in at the gas station. I see some threads about this issue, but not much, so I'm confused if it's a serious problem and adding a vent from the top of the tank to the top of the filler neck is a must do fix.

I added a vent to the top of the tank that runs to a tip over valve located on the opposite side as the fill hole up near the top of the frame. It works great for fast fills and prevents fuel spills in the event of a turn over.

I do how ever drive and R model only on the track so take that into account

[Hojo]

Okay, here’s my amateur solution. I’m in Massachusetts and have to be inspected by the smog Police. I talked to the inspector while I was plumbing the gas tubes. He said that I was exempt from today’s standards because my donor was a 2003. All he wanted was to see that I used the charcoal canister. The center connector on the oval fuel pump tank plug is labeled “ vent”. I ran a hose from it to the passenger side top strut where I had attached the canister. There are 3 tubes coming out of the canister, 2 on one side and 1 on the other. I attached the hose from the vent below to the single tube. On the other side, I capped one tube and attached a short hose and a small air filter on the other end.

When filling the tank, air goes out of the tank, through the charcoal and out into the engine bay. As the tank empties, the path is reversed. This seems to work just fine. I bought a new charcoal filter for $30.00 and a small air filter for $8.00 on eBay and had the clamps and hose lying around. I’m putting this out there so our engineers and smart people can let me know if I’m going to be blowing something up. Oh, I forgot to mention that I also mounted a fire extinguisher on the firewall between the seats.

[Bicyclops]

Did adding a vent allow for filling the tank without problems? I'm building an S and really don't like the filler location so low on the tank. I'm thinking about putting a doghouse on the top and covering the existing filler location. Is welding on the existing tank feasible?

Ed Holyoke

[TheHelixx]

I added one in the new style tank. I picked up a bulkhead and a 90 degree fitting from Summit. It Just clears the firewall and was pretty easy to add. That is if you don’t already have the tank covered and or have fuel in it. If you do add it, use a step drill as drilling holes in sheet metal that big will tear with a regular bit. I drilled it above the filler barb so I could access the inside nut through it with a ratchet. Use a cup inside to catch the metal shavings or a magnet. I don’t have a pick of the MacGuyver trick... Basically I wadded you a small piece of tape in a socket and placed the nut and Deleon washer on top. Then wrapped the socket and washer with tape to hold it in place until I got the threads started.

C6F04DFA-D4AE-4648-85AC-40E6ED443D93.jpg 03026572-AE98-4463-B29F-BBEB81C5950A.jpg 18A3F69A-6A55-4C0D-895A-A95901C438A6.jpg

[Hobby Racer]

Did adding a vent allow for filling the tank without problems? I'm building an S and really don't like the filler location so low on the tank. I'm thinking about putting a doghouse on the top and covering the existing filler location. Is welding on the existing tank feasible?

Ed Holyoke

Yes, a vent allows for fast fill ups and yes you can weld on the FFR tank, its just mild steel. Be sure of course that it has not had gas in it yet

[flynntuna]

https://thefactoryfiveforum.com/show...el-tank-issues

Here is a link to an old thread that could be useful.

[Dave 53]

The set up I had from previous owner... The right side smaller fuel tank cover has a single tube barb and fuel gauge float. This barb is a 1/4" tube that goes to near the bottom of the tank, so it's not a vent. Previous owner capped it. Left side main tank cover has 3 barbs. Fuel out, fuel return and 5/16" vent. Previous owner had the 5/16" vent connected to a charcoal canister with a 1/4" barb effectively making the ONLY venting via a 1/4" system. Fine for slow fuel level changes during burn off and temperature changes, but a 1/4" vent is nothing when filling the tank at the pump.

What I did... Turned the 1/4" tube on the left side tank cover into a vent. The tube can't be cut because it is part of the float mechanism, so I drilled holes into the top of the tube. Since this is a 1/4" tube, I connected it to the 1/4" charcoal canister. The 1/4" hose runs up to the top of the firewall before going down the the charcoal canister. This loop keeps liquid gas from making it into the canister. When I read stories of cars at the gas pump leaking gas out the vent, it's probably because the vent hose never makes a loop that is higher then the gas cap. The charcoal canister is mounted on the bottom of the chassis so the vent out is at the same level as the bottom of the gas tank. This way, if the car is upside down, gas won't leak out.vent holes.jpg

The fuel fill neck is 304 stainless steel. Found a 304 SS bung on Amazon and had a friend weld it onto the top of my fuel fill neck. Threaded in a 5/16" hose barb and connected that to the 5/16" tank vent on the main tank cover. Since this vent is inside the fill neck, it only works as a vent when filling at the pump. Not an issue if the car is upside down. Make sure the hose run doesn't have a dip in it that gas could pool in. neck bung.jpg

Now, with the gas cap on, the car has a 1/4" vent which is fine. When at the pump with the cap off, it has a 1/4" vent plus a 5/16" vent which should allow for fast gas station filling. The surface area of a 1/4" circle is .05". The surface area of a 1/4" circle plus a 5/16" circle is .40". 8X improvement in vent surface area!

No need to mess with drilling a hole in the gas tank.

[Mechie3]

I have a completely custom tank, but I added an internally closed vent. What I mean is, the top of the tank vents to the side of the fuel filler neck (also a custom piece to add a fitting). When the fuel cap is in place, the vent is now part of a closed system. When I'm filling, it allows air to flow out at a point higher than the gas nozzle.